Sabot retainer



United States Patent 2,993,444 SABOT RETAINER Charles E. Hablutzel, Albuquerque, N. Mex., assignor to the United States of America as represented by the Secretary of the Navy Filed Aug. 2, 1945, Ser. No. 608,598 2 Claims. (Cl. 10293) This invention relates to projectiles for guns and, partioularly, to sub-caliber projectiles which include a releasable sabot.

In projectiles having a sub-caliber core and a releasable sabot, a difficulty frequently encountered is that of holding the component parts of the projectile together prior to loading into the gun, without impairing proper release of the sabot after firing. This difliculty was to a degree dealt with in some cases by assembling the projectile parts somewhat loosely. In such projectiles, however, considerable trouble is sometimes encountered in handling, as in packing operations at the factory or while unpacking or loading in the field. Unless particular care is observed, the component elements frequently separate, in which event it is easily possible that some of the elements will be lost or damaged. At best, considerable time must be consumed in reassembling the separated elements, and in service use this is a serious disadvantage. Even where provision is made for positive retention of the projectile parts, a further problem arises in obtaining release of the sabot early in its flight after firing.

Accordingly, an object of the invention is to provide a projectile in which a sub-caliber core and a sabot are locked in assembled relationship, the sabot being releasable after the projectile is fired without deflecting'the core from its established flight path, but being firmly held on the core prior to firing.

Another object of the invention is the provision of a projectile in which a sub-caliber core and a sabot are positively held in assembled relationship in such a manner as to overcome the above described difliculties, and are conditioned for separation under shock, heat, or centrifugal force, all of which are natural consequences of firing a projectile. A further object of the invention is to provide a proecticle of the character referred to above which is simple to manufacture and is adapted to large quantity production.

Other and ancillary objects and advantages of the invention will be apparent from the following specification and the accompanying drawing in which:

FIG. 1 is a side elevational view, partly in section, of a preferred form of the invention;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1;

b FG.3 is a longitudinal-sectional view of the rotating FIG. 4 is a longitudinal-sectional view of the forward bearing ring;

FIG. 5 is a side elevational view, partly in section, of a modified form of sub-caliber projectile, showing one form of sabot retaining ring covered by the present invention;

FIG. 6 is a plan view of one form of sabot retaining ring of the present invention;

FIG. 7 is a plan view of another form of sabot retaining ring.

The projectile assembly in the form illustrated includes a substantially cylindrical sub-caliber core and a sabot in the form of a cup or base plate fitting about the rear portion of the core and locked to the core by means of a retaining ring which is destructible under at least one of the conditions incidental to firing a projectile from a Referring to FIGS. 1 through 4 of the accompanying 2,993,444 Patented July 25, 1961 drawing, the projectile there shown comprises a sub-caliber core 11 having an ogive nose portion 11a and an axially extending rear hub or fuze plug 12 of reduced diameter which may be integral with the core or suitably secured thereto. An elongated cylindrical bourrelet 13 which may be made of reinforced plastic, dural, light metal, fibre, or the like, is mounted on the body of the core over most of the core length except for the ogive portion. In order to prevent the bourrelet from sliding forwardly over the ogive of the projectile core during handling, there is preferably provided a stop 14, which, as shown in FIG. 1, comprises an annular shoulder on the projectile core immediately in advance of the bourrelet.

A sabot 16 fits loosely over the hub 12 and is held firmly against the rearward face of core 11 by retaining ring 17 threaded to the rearmost end of hub 12. A rotating band 18 of copper or other suitable material is mounted by press fitting or by other suitable means in annular grooves 18a on the periphery of the sabot. The retaining ring 17 presses against the sabot 16 and holds the sabot and sub-caliber projectile firmly together. The sabot extends over the rearward end of the bourrelet as shown and effectively retains the bourrelet in snug contact with the sub-caliber core 11. Ring 19 of steel or other suitable materials is threaded on the forward end of the bourrelet 13 and acts as a front bearing surface between the bourrelet and the gun bore.

If desired, the bourrelet 13 may contain longitudinal slots 20 dividing it into three or more segments, the segments being held together on the sub-caliber core in front by the bearing ring 19 and in the rear by sabot 16 which, for the purpose, is recessed to form an annular retaining shoulder 16a. Alternately, slots 20 may be terminated at a distance from the rearward end of bourrelet 13 leaving an uncut portion (undesignated) to break under the centrifugal force which is imparted to the projectile by the rifling of the gun barrel when the projectile is fired.

The projectile depicted in FIG. 5 is similar to that shown in FIG. 1 and contains substantially the same parts with the exception of the forward bearing ring 19. The sabot retaining collar employed in this modification, how ever, is somewhat different in design from that shown in cross-section in FIG. 1, and is illustrated in plan view in FIG. 6. The collar 21 has a taper 22 adapted to cooperate with a corresponding inward taper of a reces in the rear sabot surface when the collar 21 is threaded tightly upon hub 12 of core 11. The collar is composed of a combustible material, for example, magnesium, and is adapted to burn rapidly upon contact with the hot gases of combustion of the propellant powder. This burning is hastened by the concentration of the flame by the inward taper of the sabot recess 22a. This taper is a funnel, in a sense, which not only directs the force of the blast on the base of the core but also focuses the heat on the burnable or fusible retainer 21. To the former end a chamber 23a receives some of the pressure by way of the perforations 23. The chamber is formed by the outer wall of a central opening at which the taper 22a ends, together with the adjacent surface of the base and by the collar 21 which stops short thereof. Perforations 23 are provided to expose a greater surface of the collar 21 to the hot gases, thereby assuring more rapid destruction of the collar by burning. These perforations also provide convenient holes for a spanner wrench when used to screw the collar home.

Another modification of the sabot retaining ring is shown at 24 in FIG. 7. This ring is composed of steel or other such relatively strong material but is greatly weakened by a complete break 26 and a notch 27 located diametrically opposite the break. The ring 24 is sufficiently rigid under static conditions to secure the sabot and the bourrelet against any relative movement with respect to the sub-caliber core in ordinary handling or loading operations. Upon firing of the projectile, however, the centrifugal force imparted to the projectile .causes the ring 24 to open at its point of the break 26 to release the sabot and the bourrelet from the core. The opening action of the ring is greatly facilitated by the notch 27 this results in almost immediate detachment of the ring and, consequently, the sabot and bourrelet, after the projectile has left the muzzle of the gun.

When the sub-caliber projectile is fired from a gun, the rotating band 18 engages the rifiing of the gun barrel, and, due to the high pressure of the sabot 16 against the core 11, the rotation imparted to the rotating band is in turn transmitted by the sabot to the core. Proper axial alignment of the entire projectile assembly within the gun barrel is maintained by contact of the bearing ring 19 with the lands of the rifle bore. The dynamic conditions set up in the projectile when it is fired, and the hot powder gases resulting from such firing, act either singly or in cooperation to release the sabot and the bourrelet from the sub-caliber core immediately after the projectile has emerged from the muzzle of the gun. This separation can occur in a number of different ways some of which will now be given by way of illustration. When the sabot ring, for example ring 21, is composed of a combustible material such as magnesium, the hot gases of combustion of the propellant charge cause the ring to ignite immediately upon firing. The ring is thus quickly destroyed releasing the sabot and the bourrelet which are swept from the core by wind resistance or thrown therefrom by centrifugal force. When a loW melting substance, such as lead or any of the well-known fusible alloys, is used in the ring composition, releasing action of the sabot and bourrelet from the core is effected by melting the ring in the hot gases resulting from combustion of the propellant. In the foregoing two modifications of the sabot retaining ring the melting or burning action of the ring is greatly facilitated by the presence of a number of perforations 23 in the ring permitting greater access thereto by the hot gases. Of course, where the substance of the ring is both combustible and fusible, both of these effects will cooperate to bring about an even quicker destruction of the sabot retaining ring, and such action is contemplated by the invention.

Other modifications of the invention include sabot retaining rings composed of low-strength substances, such as plastics, which disintegrate upon firing, or sabot retaining rings composed of relatively strong material, such as that depicted in FIG. 7, but which are deliberately weakened to cause their disintegration under centrifugal force.

While what has been described is particularly illustrative of a presently preferred embodiment of my invention, it is not intended that the scope of the invention be limited thereto but that it embrace any modifications and changes which fall within the true spirit of the invention, as covered by the appended claims, occurring to those skilled in the art.

I claim:

1. In a projectile, a sub-caliber core having a base with a rear center protrusion, a sabot having a funnel-shaped recess terminating in a central opening defining the outer wall of a space walled at the front by the base against which the sabot is fitted, and a member having a taper matching the recess driven onto the protrusion to jam the sabot against the base with said member stopping short of the base to complete the space into a chamber, said member having perforations communicating the recess with the chamber and being composed of material disintegrable by the heat of a projectile propelling explosion having access to the surfaces of the member through the funnel shaped recess and the perforations.

2. In combination with a projectile having an after sabot securing extension, a sabot having an outer cylindrical surface and an inner surface of the configuration of a frustum of a cone, said inner surface at the uppermost portion thereof surrounding said extension, and a heat disintegratable tightening collar interengaged with said extension and having its undersurface tapered to wedge against the uppermost inner surface of said sabot so as to force the sabot against the projectile upon tightening, said collar having openings therein to permit heat and pressure to reach added surface area of the collar to expedite the disintegration of the collar, said inner surface of the sabot serving the additional function of directing and concentrating the heat of the projectile propelling explosion onto the collar.

ReferencesCited in the file of this patent UNITED STATES PATENTS 

